1. Field of the Invention
The present invention relates to engine load control means and more particularly to means for controlling engine load so that a decrease in the engine speed can be avoided when an electrical load is applied to the engine. More specifically, the present invention pertains to means for controlling load on an engine having an electric generator.
2. Descriptions of Prior Art
In vehicle engines, problems have been experienced in that the engine speed is abruptly decreased when a load is applied to an idling engine by for example turning an air conditioner on or moving the shift lever of an automatic transmission to a driving range. Such a decrease in the engine speed causes an engine stop or rough engine operation. In order to avoid such problems, it has been proposed to change the engine operating conditions by for example increasing intake air flow and/or fuel supply.
For example, in Japanese patent application No. 53-5362 filed on Jan. 20, 1978 and disclosed for public inspection on Aug. 3, 1979 under the disclosure number 54-98413, there is disclosed an engine control system which includes an air passage bypassing the throttle valve. A control valve is provided in the air passage for opening the passage when a load is applied to the engine so that an additional air supply is made through the air passage.
It should however be noted that the conventional system is not satisfactory since there will be delays in the operations of the control valve and the engine. As soon as the load is applied to the engine, a signal may be produced for operating the control valve, however, there is a mechanical delay in the operation of the control valve. There is also a certain time delay before the engine speed can increase after the additional air supply is actually started. Thus, the engine operation cannot rapidly follow the increase in the load and there may still be a risk that the engine speed is decreased to an unacceptable value. It may therefore be a way to delay the start of operation of the load until the engine speed is sufficiently increased. However, the solution is dissatisfactory because it is always not preferable to delay the operation of the load. Further, in case of shift levers for automatic transmissions, it is impossible to delay the load of the transmission incurred on the engine after the shift lever is moved to a driving range.